High-speed geid camera



Sept. 29, 1953 l. M. RlLEs ErAL 2,653,507

HIGH-SPEED GRID 4CAMERA Filed Sept. 16, 1949 7 Sheets-Sheet l www@ Sept.29, 1953 1. M. RILEs ET A1. 2,653,507

HIGH-SPEED GRID CAMERA Filed Sept. 16, 1949 'I' Sheets-Sheet 5 Sept. Z9,1953 l. M. RILES ET ALAl HIGH-SPEED GRID CAMERA 7 Sheets-Sheet 4 FiledSept. 16, 1949 sept- 29, 1953 1. M. RILES ET Al. 2,653,507

HIGH-SPEED GRID CAMERA Filed Sept. 16, 1949 7 Sheets-Sheet 5 lrraa/vrSept. 29, 1953 Filed Sept. 16, 1949 l. M. RILES ET AL HIGILSPEED GRIDCAMERA 7 Sheets-Sheet 6' Sept- 29, 1953 l. M. RIU-:s ET AL 2,553,507

HIGH-SPEED GRID CAMERA Filed Sept. 16, 1949 Sheets-Sheet 7 PatentedSept. 29,h 1953 UNITED STATES PATENT OFFICE Stratton,

Inglewood, Calif.,

assignors to Northrop Aircraft, Inc., Hawthorne, Calif., a corporationof California Application vSeptember 16, 1949, Serial No. 115,972

2 Claims.

This invention relates to movie cameras and more particularly to ahigh-speed, grid camera useful for tracking purposes.

In cameras to be used for photographing moving objects, such as testmissiles, for example, it is desirable, when the camera is running, tobe able to readily change the lm frame speed while still maintaining a`desired rconstant iilm exposure time.

By this means, during photographing of test work for example, theoperator is enabled to increase the speed of the camera if some actionof unusual importance happens to the object being photographed. Thus, aslow motion study of this action is made available which may1 be ofgreat help in determining its cause.

Furthermore, by being able to change the iilm frame speed of such acamera, at will, a great saving in lm results, since, if the camera lhadto be running at high speed for an entire test in order to ensuregetting the detail of the crucial action, most of the lm may have beenused for photographing unimportant actions.

`Moreover, running at high speed for the entire length of a test usesiilm up rapidly, hence the present invention permits a relatively longerrunning time for one film loading of the camera.

In high speed test cameras it is further desirable to be able tosuperimpose onto the film a reticle or grid. Thus providing means forpositively identifying the position and movement of objectsvphotograplfied with respect to known reference points.

When attempting to orient objects by such means to a high accuracy, itis very important that the grid lines superimposed on the lm bemaintained extremely accurate, since even slight aberrations in theirrelative relation, such as due to temperature effects, can causeappreciable error in the tracking data.

Among the objects of this invention are:

To provide a novel relative arrangement of parts for providing a highspeed tracking camera.

To provide a novel means for lmaintaining a constant exposure time whenthe film frame speed is varied while running la movie camera.

To provide a novel means for varying the shutter opening of a moviecamera.

To provide a novel means of indicating accurate orientation in space ofobjects photographed by a movie camera.

To provide a novel optical arrangement in a movie camera for reiiectinga reticle onto the image plane.

Briey, this invention consists of the construction, combination,location, and relative arrangements of parts for obtaining a high speedmovie camera. In the preferred embodiment of the invention, "a rheostatcontrolled motor is provided for actuating a mechanism whichintermittently feeds the film past a nlm gate in the camera box. Avariable shutter is provided for controlling the opening time of rthe lmgate. A planetary gearing system, driven by the motor, rotates ltheshutter and provides the means for varying the aperture of the shutter.An external control means is yconnected to both the rheostat and theplanetary gearing system of the shutter in such a manner that a singlead- J'ustment of the external control means enables a lconstant exposuretime to be maintained while the film speed is being varied. The externalcontrol means can also be adapted for permitting independent regulationof the rheostat and the shutter aperture.

In addition, a reticle constructed of a low expansion alloy is somounted in the camera that it remains stationary while the camera boxand the associated attachments, including the objective lens, sweep thearc of the reticle. Graduations marked on the reticle are reflected byan optical arrangement, also moving with the camera box, so as to besuperimposed on the film frame along with the image of the objectv beingphotographed.

This invention can be more fully understood by' reference to thedrawings, 4in which:

Figure 1 is a side view of the preferred embodiment of a high-speed,grid camera mounted on a tripod and showing the general arrangement ofthe attachments on the camera box.

Figure 2 is a top view of the camera box showing the arrangement of theattachments.

Figure 3 is an elevation cross-sectional view of the camera box taken atsection A-A of Figure 2 showing the arrangement of the camera drivingmechanism, the reticle assembly, and the reticle reflecting system.

Figure 4 is an inside plan View of the upper half of the camera boxshowing the lm driving mechanism and the path the lrn takes through thecamera.

Figure 5 is a detailed plan view of the reticle plate.

Figure 6 is a top view of the reticle as shown in Figure 5.

Figure 'I shows the side view of the shutter assembly as mounted in theoptical path of the camera.

Figure 8 shows the location of the film gate with respect to the shutteraperture.

Figure 9 is an exploded view of the shutter assembly showing, inparticular, the planetary gear drive system.

Figure 10 is a plan view of the lower half of the camera box showing thepulley drive arrangement.

Figure 11 is a cross sectional view of the double control knob.

Figure 12 is a plan View of the control knob showing the calibrateddial.

Figure 13 is a view of the shutter pulley drive taken at line B-B ofFigure 10.

Figure 14 is a View of the rheostat pulley drive and roller guides astaken at line C-C of Figure 10.

Figure 15 is a graph illustrating how the lm speed is made to vary withthe shutter aperture to give a constant exposure time.

Referring first to Figure 1, a preferred embodiment of the high-speed,grid camera is illustrated. Here the camera l is shown to be mounted ona cone shaped mount 2 which in turn rests on the friction head 3 of atripod fi. A locking nut 5 is used for locking the camera l to thetripod li. The legs of the tripod t are made adjustable in height byknurled collars S. The tripod i is preferably xed in position and wellanchored at the base shoes .Ei so as to provide a reference base for thecamera indexing. Two bubble levels 5 placed at 90 with respect to eachon top of the camera, help in positioning the camera. Y

TheV high-speed camera is made up largely of the main housing or camerabox i2 with the necessary accessories attached thereto. These latter, asshown in Figures l and 2, are conventional components and include thevariable lens focussing assembly i3 mounted horizontally on the front ofthe camera; the film drums ida and Mib, held by a drum bracket 2l, andpositioned horizontally with respect to a shelf it provided at the rearof the camera box l2 a tracking viewer il attached to the near side; anda ventilated rheostat I8 attached to the far side of the camera Y boxl2. Rheostat iB is mounted in such a manner that it is removable tofacilitate putting the camera in its carrying case. Y

As shown in Figure 1, a motorie having a hand positioning knob 2dextends downward Slightly below the bottom of the box l2. Motor i9,whose speed is controlled by therheostat i5, feeds the lm from the filmdrum ldd past the image plane provided in the interior of y.the camerabox'lZ by lens assembly I3.

A double control knob assembly 22 is provided at the rear of the camerabox l2. This control assembly knob 22 provides the means for changingthe lm frame speed of the camera while still maintaining a constantexposure time for the film as will be explained in the ensuingdiscussion.

An electrical lead 23 attached to the bottom of the camera box i2 feedsthe necessary D. C. voltage required by motor IS. An initiating switch2d, located below control knob assembly 22 energizes the motor I9 forstarting the camera running. Y

Figure 3 shows an elevation view of the camera box l2 taken at sectionA-A of Figure 2. A main baise plate 25 having the general contour of thedetachable top 25 of the camera box i2, except for a cut-out at thefront for accommodating a shutter, is mounted inside the box i2.

4 In order to facilitate servicing the camera, all the gearing and filmactuating mechanisms are so arranged that they can be mounted onto themain plate 25 outside the camera and inserted into the camera box as aunit. The main base plate 25, in general, divides the box horizontallyinto two compartments.

The top compartment of the box l2 is in line with the image optical pathof the camera and contains the hlm guiding and moving mechanism. Thebottom compartment contains the camera driving mechanism, the reticlearrangement, and the main bearing mount.

As shown in Fig. 3, the motor I9, which is a direct current intermittentduty motor is almost entirely enclosed within the camera box l2. MotorI9 is controlled by two rheostats I8 mounted in tandem. One rheostatcontrols the field and the other controls the armature of the motor Itto give a speed variation of from 950 to 9600 R. P. M. Motor il? isattached by screws 2'! to a bracket 29. Figure 4 shows the plan view ofthe bracket 29 and indicates that it is suspended below the main baseplate 25 by lugs 30 located at each of its corners.

Two shafts, the film drive shaft 3i and the drum drive shaft 32 extendupwardly from the base of the bracket 25 and have their lower endsrotatably mounted therein by roller bearings 33. A film drive gear 3d iskeyed to the lower portion of the nim drive shaft 3i and is driven bymotor pinion S5 of motor l. Film drive shaft 3i extends through the mainbase plate 25. An attachment plate 55 secured to main base plate 25contains a second roller bearing 3l by which the central portion ofdrive shaft 3l is rotatably supported. On the fianged upper end of filmdrive shaft 3l a lm sprocket 3S is held, just above main base plate 25,by round head screws S5. Film sprocket 3S rotates at one-eighth thespeed of the motor I9.

Film drive gear 3ft meshes with a pinion di] on a drive shaft di of ahigh speed movement unit 2, thus the drive shaft il rotates at a 1:1ratio` with the motor l. The movement unit d2 is of the conventionalcyclic film feeding type which moves a feed-length of the lm Itintermittently and holds it in position at a film gate 33 for theexposure of each film frame. Film gate d3, rectangular in shape, isprovided in a iight shield ifi attached to the main base plate 25; andis positioned in the image plane of the focussing assembly I3. A flywheel 'i5 for the movement unit i2 is attached to the lower end of themovement drive shaft lil.

A drum drive gear lt, similar to film drive gear 3ft, Vis keyed onto nlmdrum shaft 32. Gear 5d enables shaft 372 to be driven by motor pinion35. A spacer d5, mounted in a support i? placed below the main baseplate 25, and a ring d8 locate a drive pulley above the drum driver gear5d, on the drum shaft 32. A small upper bearing 5t attached below mainbase plate 25 supports the upper end of drum shaft 32.

The take-up spindle 5i for the film it has a takeup sheave 52 which isjoined to drive pulley dii by a tension belt 53. As shown in Figure 4,tubes l5, passing through the back wall of camera box l2, guide thetension belt 53 along its Path.Y Y

Roller guides 55 for the film l5 extend upwardly from a cover 57 whichis attached to the main base plate 25 above the drive pulley Vlid.

Figure 4 shows the path the film takes through the camera. The 35 mm.nlm it is drawn from the 1000 foot feeding drum Ma past felt coveredintake rollers 150 provided in Idrum bracket 2|. Intake rollers ld areplaced close to the lm opening H provided in vthe rear wall yof thecamera box i2, and the felt covering ensures that the opening I5! islight tight. The film IU lis then fed through the roller guides 55 tothe movement unit 4E by the teeth on nlm sprocket 38. The hlm i9 is heldagainst the teeth of film sprocket 38 by two sprocket kguide assemblies59. An electrically connected trip mechanism (not shown) is provided tostop the camera irnmediately in case of film breakage.

This completes the description of the film guiding and feedingmechanism.

Referring back to Figure 3, the reticle vassembly v58, its Aassociatedoptical reidecting system, and the main bearing `mount is also shownthere. The main bearing mount comprises an upper and lower race plate 6Ivand 62, respectively, and an outer race plate 55. Reticle plate k6),which holds the reticle 55, is positioned near the inside bottom ofcamera box l2 and rests by a boss Sila on the upper race plate 6l towhich it is attached. The circular extension of upper race plate `6| isthreaded so as to engage the internal thread of lower race plate 62 thusforming the complete inner race for the main bearing. Lower race plate82 is then rigidly attached to the flange of cone-shaped mount 2 by fiathead screws 63.

The outer race plate 55 is securelyattached to the bottom of camera boxI2. The inner periphery of the outer race plate 55 is so beveled that itrides on bearing balls `ft positioned between the upper and lower races5I and 62. Thus, the camera box is enabled to be rotated in azimuth.

The reticle plate 60, the upper race plate 6| and the lower race plate62 all have a central circular hole 64 therethrough concentric with theazimuth rotating axis of the camera. The bottom of motor i9 extendsfreely through this hole 64, thus enabling the camera box, to which it`is fixed, to rotate with respect to the stationary1 reticle assembly 58which, as described, is fixed to the tripod 4.

Itis to be noted that an annular piece of felt 28, or similar resilientmaterial, is used to prevent light from entering the camera box throughthe clearance in circular hole 64. Likewise, the entire camera box ismade light-tight throughout.

The friction adjustment knob 65a is mounted on the flange of the coneshaped mount 2 on the bottom of the camera. Knob 65a is comprised of aspring loaded cork friction plate, with adjustable tension, and is usedto vary the freedom `with which the camera can be rotated about itsazimuthal axis, or to hold the camera stationary.

Reticle 55 as shown in detail in Figures 5 and 6 is in the shape of a180 circular arc and is preferably made integral with the reticleplatef50 so as to provide a rigid structure. The reticle ar-c 55 isymachined so that it is held to be `concentric with the boss 60a of theplate B0 by which it is held in the vazimuth axis of the camera. Anextremely accurate grid is engraved on the chemically blackened face ofthe reticle 55. The .001 inch engraved lines are graduated infdegreesazimuth and zenith. It is indexed from 0 to 180 in azimuth and isheld towithin 15 to the center or 90 point, i. e., the tolerance is notaccumulative. The graduations are designated every five degrees fromboth ends of the arc. The grid is indexed for a 5 degree range inzenith. Thefre'ticle 55 and its base plate 50 is made from a, .low

6. expansion alloy to ensure that temperature effects do not causedeviations in the grid to be reflected onto the lm 10.

The reticle reflecting optical arrangement (Figure 3) for transposingthe image of the reti- .cle onto the lm i0 is .located near the front ofthe camera box l2 and consists of a 45 prism E6, a collimating lens 56a,and a half silvered optically flat .glass i mounted together in anassembly such that their total reflecting angle is The prism 15S ismounted on the inside front wall of the .camera box l2 so as to pick upa portion rof reticle 55 and reilect it through the collimating lens Staonto a glass 67 which is located in the optical path of the objectivelens of the focussing assembly I3. Flat glass 61 reflects the image ofreticle 55 onto the film I0, at the same time allowing the subject imagefrom the objective lens to project -through and onto the film. The lightsource for the reticle 55 is a 50 C. P. lamp G9 mounted directly belowthe optical arrangement.

A removable plug id in the camera box top 26 above the flat glass El isprovided for enabling the operator to visually check the images to bephotographed.

The shutter assembly l0 for the camera is positioned in the camera boxl2 with respect tothe lm gate i3 as shown in Figures e, 7 and 8.

The shutteiassembly l0 is held just below the main base plate 2E by abearing and coupling gear support 'H near the front of the shutter shaft72, and a smaller bearing support 'I3 near the outer end of the shaftl2, as best shown in Figures 4 and 7.

A helical gear 'l5 on the main film drive shaft 3l (Figure 3) mates witha helical pinion 'it on the shutter shaft l2 (Figure '7) to form adirect right angled drive for the shutter assembly 70. The ratio of theshutter shaft 'l2 to the movement drive shaft 4| is 1:2.

The shutter is a double rotary disc, a and 71h, arrangement with fourequally spaced 2l/2 apertures 18 in each disc. These apertures 18 aredefined by an inner and outer arc and the portion of the radius betweenthe arcs. The shutter discs lla, 'Hb are positioned so that thediagonally opposite corners of the rectangular film gate e3, as shown in1Figure 8, are just enclosed by the inner and outer arc of the apertures13. The two shutter discs ila, 'Hb are synchronized with the nlmmovement unit t2 so that, when the apertures 'it of the Shutter are infront of the film gate 43, the nlm it is at rest. The nlm moves when theopaque portion of the shutter discs cover the gate.

Referring to Figure 9, an exploded detailed view of the shutter assemblyl is illustrated. There, the shutter shaft 'F2 is shown to have thehelical pinion 7S near its rear end held by a key 79. The assembly 'i0is driven by this pinion as previously noted. Near the front end of theshaft l2 a needle bearing SI is tted onto its first shoulder 82 by whichthe shaft is held in bearing and gear support 'il to be attached to themain base plate 25. A step-down gear 83 is held onto the next shoulderS4 by a modified key 85. The shutter shaft 'i2 is coupled to drive therear shutter gear d? of the shutter drive unit through a compound gearte which is held by the threaded end of its hub 50 and the nut 85 in thebearing and gear support il. The gear relationship for these couplinggears is such that the shutter shaft 'l2 rotates twice as fast as therear shutter gear i. The rear shutter gear t? is Lriveted to the rearshutter disc lla by rivets 7 89. A sleeve bearing 9U held by a key Si tothe inside diameter of the rear shutter gear 81, enables gear 8l to berotatably mounted on the shutter shaft 'l2 which extends therethrough.

A housing 93 has its base riveted to the front disc lll) of the shutterassembly by rivets 92. A housing top 9i is held onto the base of housing83 by screws itil. Housing S3 encloses the planetary gearing systemwhose gear arrangement is such that it not only rotates the frontshutter disc l'ib at the same speed as the rear disc lla but in additionenables the discs lla, 1lb to be moved relatively with respect to eachother to change their combined aperture opening. A planetary drive gear9d is press itted onto the front end of the shutter shaft 'l2 whichfreely extends through both discs lla, l'lb, and through a bushing le@provided at the axial center of the base of housing 93. Two idler gears95a and bh, located diametrically opposite each other, are driven by theplanetary drive gear Slt. These idler gears alla, iib are rotatablymounted on idler pins 9de and @to held between the top Sl and theintegral base of the housing Q3 at a ixed radius from the center oirotation of the shutter assembly. The heads of pins 95a, 95h arethreaded to engage the base of the housing 93. Cut-out holes Si?, in theiront and rear discs enable the pins Qta, @5b to pass therethrough forease in assembly.

Two compound spur gears Qta' and 9th are similarly held in the housing93 by pins lilla and lllib located at a radius from the center ofrotation of the shutter assembly lili. Each oi the compound spur gears@du and 99'@ is in such a position that its rear half can be driven byone of the idler and 'ib, respectively.

At the axial center of housing top tl a bearing MEE is provided in whichin journalled the hub of an adjusting gear 03 which is located justinside the housing 93. Adjusting gear 53 meshes with both the fronthalves ci compound spur gears @da and @9b.

A shutter pulley lil is attached outside housing 93 onto the outwardlyextending hub of adjusting gear itt by a square key itt. On the rearside of adjusting gear 483 a thrust ball bearing lill is seated forrotatably supporting the reduced diameter front end of shutter shaft l2.

Thus it is noted that as the shutter shaft l2 is rotated both discs lla,llt are driven together at the same speed as a unit.

The rear disc lla. riveted to the rear shutter gear ill is driven bystep-down gear 83 on shutter shaft l2 through the compound gear til; andthe front disc lb is driven through the planetary drive gear Slt onshutter shaft l2, then through the planetary idler gears sda and @Libwhich in turn drive the compound spur gears tta, Stb respectively torotate the housing 93 (to which the front disc "Vb is riveted) at thespeed with which the center of spur gears Qta, 9th rotate about thenormally stationary adjusting gear m3. When- Y ever it is desired tochange the combined aperture opening or the shutter, i. e., change theposition of the discs 'llc relative to each other, an incrementalrotation of adjusting gear HB3 by a shutter pulley it causes thecompound spur gears tta and lb to rotate on their pins lilla, lilib withrespect to the housing 93 and hence rotate the front disc 'lib withrespect to the rear Vdisc lla. Dependent on whether this incrementalrotation is additive or subtractive to the already existent rotation ofthe center of spur gears 93a, 99D about the shutter assembly axis, theaperture increases or decreases. The use of a 4 to 1 gear ratio betweenthe movement drive shaft 4|, which drives the movement t2, and thefourapertured shutter discs 11a, lb results in four film frames comingup for exposure each revolution of the shutter assembly, i. e., each oflm frames is exposed for the time duration determined by one of thevariable apertures 18.

The pulley and cable arrangement for changing the shutter apertureindependently or in accordance with the nlm frame speed will next bedescribed.

As shown in Figure 10` a view of the lower-compartment of the camera boxreveals the two sets of cable arrangements, leading to both the shutterpulley m5, just described, and a rheostat pulley H19 for adjusting thefield and armature of the motor I9. Rheostat pulley m9 is held to theside wall of the camera box l2 by a rheostat bracket 124. The two setsof cables are tied in together by the double control knob assembly 22.The arrangement of the cables and their connections is such that they donot interfere with the removal of the main boss plate 25,

A cross sectional View of the double control knob assembly 22 is shownin detail in Figure ll. The outer control knob l it, known herein as theshutter control knob, is held by a square hole in its center onto thesquare cross sectional end portion of the shutter control shaft lll by aretaining nut H2. The inner control knob H3 herein designated as therheostat control knob, also is held by a square hole in its center whichmates with the squared outer surface of a hollow rheostat control shaftlift whose inner sur face freely rotates about shutter control shaftill. Rheostat control shaft lill is journalled in a bearing i i5 mountedin the rear wall of camera box l2. Immediately, on the inside end ofrheostat control shaft llt, a rheostat drive pulley H5 is attached. Asshown in Figure l0 an endless cable drive HVB is used for transferringthe rotation or rheostat control shaft lid, along the inside contour oithe camera box l2, to the rheo stat shaft Hl. The cable H3, makes atleast two complete revolutions about the vertical rheo- Y stat drivepulley Il@ in order to ensure that no slipping occurs.V The upper andlower ends of the cable HS are then curved at almost a right angle atthe inside corner of the camera box I2 by a double horizontally arrangedPulley assembly Ils attached to the side wall oi the camera box. Thecable H8 then is guided through a secondV horizontal double pulleyassembly iZ which directs it onto a third vertically disposed set ofpulleys l2l which diverts the cable lit to the driven rheostat pulleyits on the rheostat shaft lll. The cable, as'before, makes at least twocomplete revolutions about the drive 'rheostat pulley m9.

The shutter control shaft lli extends horizontally into the lowercompartment of camera box l2 to terminate just under the end of mainbase plate 25. A bearing support iZS for the shutter control il! isprovided underneath th shelf VIt of the camera box l2. Near the irontend of shutter control shaft lli a worm IE5 is provided for engaging aworm wheel E26 keyed to the end of an intermediate pulley-shaft l'l. Apulley housing l2@ secured beneath the main base plate 25 provides a twobearing support for intermediate pulley shaft l2? which is verticallythe. shutter cable |30 around the two intermedi' ate pulleys |3| is suchthat, as the intermediate.'

shaft |21 is rotated, one of the intermediate pulleys |3| unwinds andthe other winds the ends of shutter cable |30. The shutter cable is thenWound. about a set of horizontal pulleys |32 which directs the shuttercable |30 at substantially a right angle so as to clear the bracket 20(see Figure 4)'. The shutter cable is then Wound around another'set ofhorizontal pulleys |133 located near the inside front Wall of the camerabox l 2. From there the shutter cable |30 is led to Wrap around thevshutter pulley |05 previously described. The pulley |05 on the shutterassembly is so rigged that it rotates at a ratio of 1 to 7 with thepulley |03 on the rheostat.

Referring back to Figures 11 and 12, it is noted that a knurl headedplunger 35 is positioned oi center on the outside of the shutter controlknob H0. Plunger |35 passes through the outer knob ||0 and the taperedend |355 of its shaft is urgingly extended by spring |31 into one of thetapered holes |39 provided inthe rheostat knob |l3. Inner knob I3 isprovided with 19 tapered holes |39, their positions corresponding to theangular setting marks indicated by the dial Dial |40 is iixed to therear Wall of the camera box: IZ and. i's positioned to bev concentricwith the double knob assembly 22.

As noted, a pointer |4| is attached to the base of the shutter controlknob lli on the same radial line with the plunger |35.

The index lines for the angular aperture set-- tings of the dial |40 arespaced in intervals of 17 30 plus or minus 15", and the tolerance is notcumulative. These index lines correspond to the fixed shutter aperturesettings at which the camera shutter can be maintained.

Referring back to Figure 4, a tachometer |43 is shown to be mounted onthe back of the camera on the side opposite the double control knobassembly 22. The body of the tachometer |43 extends under the cover |34provided on the shelf 3 of the box I2 and it is driven by a flexiblecable |44 which is coupled by coupling |08 to the rear end of theshutter shaft 12. The tachometer |43 is calibrated (not shown) toindicate the frames per second speed and the motor R. P. M. of thecamera.

Thus, when the plunger |53 is disengaged the rheostat I8 and thecombined aperture of the shutter discs Tia, '1lb may be independentlyset by the control knob ||3 and H8 respectively. When the plunger |35 isengaged, the rheostat and the aperture setting can be simultaneouslychanged to maintain a constant exposure time. These changes can be madeeither While the camera is running or standing still.

To further facilitate the operation, a frame counter |41 is mounted onthe top 23 of the camera box |2. This counter |47 is driven by a tonguedshaft |48 driven directly off the nlm sprocket 38 as shown in Figure 3.Geared 3 to 1, it records the number of frames or footage of lm used up.A reset knob |49 is mounted on the end of this counter.

Figure shows a graph that illustrates the action of the double controlknob assembly 22. rEhe ordinate of the graph corresponds to the combinedopening in degrees of the apertures of the shutter as indicated on dial|40 of the control knobs. The abscissa of the graph indicates the framesper second speed of the iilm as would be read oif the tachometer |43 bythe operator. The fractional time parameters such as 1/34 sec.,

jitsu sec. etc., correspond to constant exposure times desired for thenlm. For instance, assume that the light on the object to bephotographed and the setting of the lens focusing assembly I3 requiresthat a film exposure time of M380 second be maintained. The operatorrunning the camera, sets the frames per second to any convenient value,say, for example, 32, by turning the rheostat control knob ||3, with theplunger |35 pulled out, and observing the reading on tachometer |43.Then, with the plunger |35 still pulled out, the operator turns theshutter control knob Ilo until pointer I4| is opposite reading on thedial |40; he then locks the two knobs together by releasing plunger intothe corresponding locking hole |39.

The operator is now running the camera at point X of the 1/80 sec.parameter of the graph of Figure 15. By rotating the double control knobas a unit, the operator While the camera is running, can now change thespeed of the film at will, and the corresponding change in the shuttei'aperture will be such that the l/so sec. parameter of the graph will betraversed, thus maintaining the. desired constant exposure time for thefilm.

The extreme exposure times of the camera as obtained by the preferredembodiment of the shutter and motor mechanism is a maximum cf 1/2.,seconds and a minimum of 1/11585 seconds. These limiting exposureparameters are indicated on the graph of Figure l5. Any time exposureparameters in between these extremes can be obtained and maintained byknowing at least one pair of coordinates at which to set the controlknobs.

It is to be noted that the arrangement of the iilm drum in a horizontalposition has been made in order to place the length of the standard lmframe in a vertical position. By this means, a maximum zenith range forthe movie camera, which is primarily adapted for azimuth tracking, canbe obtained with standard components. In order to make maximum use ofthe azimuth range, it is desirable when setting up the camera to line upthe obiect to be photographed with the zero degree marking on either endof the arc of the reticle 55. This is facilitated by rcmovable plug 14placed in the camera box above the flat glass 6l on which both thesubject image and the reticle image are superimposed.

From the above description it will be apparent that there is thusprovided a device of the character described possessing the particularfeatures of advantage before enumerated as desirable, but whichobviously is susceptible of modication in its form, proportions, detailconstruction and arrangement of parts without departing from theprinciple involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has beendescribed in language more or less specific as to structural features,it is to be understood that the invention is not limited to the specificfeatures shown, but that the means and construction herein disclosedcomprise a preferred form of putting the invention into effect, and theinvention is therefore claimed in any of its forms or modificationsWithin the legitimate and valid scope of the appended claims.

What is claimed is:

l. In a movie camera, the combination of film driving and shuttermechanism including a motor for running said mechanisms, a rheostat forcontrolling the speed of said motor, a lm gate,

cyclic film feeding movement driven by said motor for intermittentlyfeeding lm past said gate, va shutter comprising two apertured rotarydiscs for controlling the opening time of said film gate, said motordriving one of said discs through a coupling gear, said motor drivingthe other of said discs through a planetary gear systern, Yan adjustinggear in said planetary system for varying the relative positions of saiddiscs, a shutter control shaft, a hollow rheostat control shaftconcentric with said shutter control shaft. a first pulley and cablearrangement for connecting said rheostat to said hollow rheostat controlshaft, a second pulley and cable arrangement for connecting said shutteradjusting gear to said shutter control shaft,v a shutter control knobxed on said shutter control shaft, a rheostat control knob xed on saidrheostat control shaft, said knobs being immediately vadjacent eachother at the ends of said shafts, and means for manually locking andunlocking said shutter control knob and said rheostat control knobwithout disturbing operation of said camera.

2. Apparatus in accordance with claim 1 wherein said means for lockingsaid shutter control knob to said rheostat control knob comprises aspring loaded plunger mounted in one of said control knobs for engagingindexing holes arcuately positioned in the other of saidcontrol knobs.

IRA M. RILES. DAVID W. STRATTON.

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